This invention relates generally to the production of carbon dioxide.
Carbon dioxide has a large number of uses. For example, carbon dioxide is used to carbonate beverages, to chill, freeze and package seafood, meat, poultry, baked goods, fruits and vegetables, and to extend the shelf-life of dairy products. It is an important environmental component in industrial waste and process water treatment as a replacement for sulfuric acid to control pH levels. Other uses included drinking water treatment, an environmentally-friendly pesticide and an atmosphere additive in greenhouses to improve the growth of vegetables.
Generally carbon dioxide is produced by purifying a waste or other stream which is a by-product of an organic or inorganic chemical process. The waste stream comprising the carbon dioxide may be condensed and then processed in a distillation column to produce the product grade carbon dioxide.
The higher is the concentration of carbon dioxide in the waste stream, the easier and less expensive is the final purification to produce commercially useable carbon dioxide and thus it is desirable to have the feed stream to a final product carbon dioxide facility to have as high a carbon dioxide concentration as possible. Indeed, it would be very desirable if the byproduct carbon dioxide containing fluid from the chemical process had a sufficiently high carbon dioxide concentration so that no further purification were necessary to produce commercially useable carbon dioxide.
Accordingly, it is an object of this invention to provide a method for producing carbon dioxide from a biological process wherein the concentration of the carbon dioxide produced is sufficiently high so as to reduce the level of, or eliminate the need for, further processing of the carbon dioxide product from the process in order to produce commercially useable carbon dioxide.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention which is:
A method for producing carbon dioxide comprising:
(A) providing to a fermentation broth comprising one or more carbonaceous species an oxidant fluid having an oxygen concentration of at least 40 mole percent at a flow rate such that the amount of oxygen provided to the fermentation broth is not more than 5 weight percent of the amount of carbon dioxide produced;
(B) employing oxygen from the oxidant fluid to promote microbial growth within the fermentation broth, carrying out fermentation within the fermentation broth, and producing carbon dioxide within the fermentation broth in a fermentation vessel;
(C) passing a fermentation broth stream out from the fermentation vessel, through a heat exchanger, and then back into the fermentation vessel in a recirculation loop;
(D) bubbling carbon dioxide out from the fermentation broth to form a gas mixture having a carbon dioxide concentration of at least 97.5 mole percent; and
(E) recovering said gas mixture as product carbon dioxide.
As used herein the term xe2x80x9cfermentation brothxe2x80x9d means a liquid medium containing microbes and one or more carbonaceous species which could be metabolized and/or fermented by the microorganisms.
As used herein the term xe2x80x9cfermentationxe2x80x9d means a biochemical process carried out by microorganisms wherein carbon dioxide is produced.